Reaction motor exhaust nozzle incorporating a fusible coolant



J. c. PROSSER ETAL 3,282,421

REACTION MOTOR EXHAUST NOZZLE INCORPORATING A FUSIBLE COOLANT Nov. 1, 1966 2 Sheets-Sheet 1 Filed Dec. 21, 1961 am y my, M m s a W. k V 0 n a z, m mm n W n M J w Z w. J an 2 4 a; a a/m 7 J Y y W W a, B Z mm? 1 y w 7 $1 w, W I IMIIM! ,fl UHW Mw 1 HW I MH u mWW Z IIIIHHH fir m ww a, fi mm Nov. 1, 1966 J, c, oss ETAL 3,282,421

REACTION MOTOR EXHAUST NOZZLE INCORPORATING A FUSIBLE COOLANT Filed Dec. 21, 1961 2 Sheets-Sheet 2 INVENTORS (/58 6. 5 205.96?

United States Patent REACTION MUTUR EXHAUT NOZZLE INCOR- PORATING A FUSIELE COOLANT Joe C. Prosser, Ladoga, and Richard H. Singleton, lindianapolis, Ind, assignors to General Motors Corporation, Detroit. Mich, a corporation of Delaware Filed Dec. 21, 1961, Ser. No. 162,311

Uaims. (Cl. 239-1273) This invention relates to a rocket nozzle construction and more particularly to a nozzle construction having a self-contained coolant.

Rocket noozles frequently operate at temperatures considerably higher than the melting temperatures of the materials with which the nozzle is lined. Some form of cooling system, therefore, must be provided to prevent the liner from burning out before the time set for termination of the operation of the nozzle. Prior nozzle constructions utilizing coolants have generally been of the liquid type requiring separate tanks for containing the coolant as well as control systems and additional hard- Wars for controlling the injecting of the coolant into the nozzle.

This invention eliminates the objections of prior cooled nozzles by providing a nozzle containing a solid cooling medium released by the heat of operation of the nozzle to flow out onto the nozzle surfaces to cool them.

More particularly, this invention relates to a cooled porous nozzle of the convergent-divergent type having a throat insert consisting of axially stacked sections of refractory metal plates separated by a solid coolant, the coolant being fusible at temperatures lower than the normal nozzle operating temperatures to flow out into the nozzle throat surface to insulate it against the exhaust gases passing through the nozzle.

Therefore, it is an object of this invention to provide a cooled porous nozzle construction wherein the coolant forms a part of the nozzle and cools it automatically without the use of additional hardware or control mechanisms.

It is a further object of the invention to provide a cooled fluid exhaust nozzle construction that is economical to manufacture due to the use of readily available refractory material forms, one that is simple in construction and yet highly reliable, and one providing excellent heat transfer to the coolant without the use of complicated control systems.

It is still a further object of this invention to provide a cooled porous nozzle construction comprising -a plurality of stacked thin annular sections enabling an easy replacement of parts and the easy and highly accurate control of the porosity of the construction.

Other objects, features and advantages will become readily apparent upon reference to the succeeding detailed description of the invention and to the drawings illustrating the preferred embodiments thereof; wherein,

FIGURE 1 is a side elevational view of a nozzle embodying the invention with parts broken away and in section;

FIGURE 2 is an enlarged cross sectional view of a detail of FIGURE 1;

FIGURE 3 is an enlarged cross sectional view of a portion of the FIG. 2 construction taken on a plane indicated by and viewed in the direction of the arrows 33 of FIG. 2;

FIGURE 4 is an enlarged sectional view of a portion of the FIG. 2 showing taken on a plane indicated by and viewed in the direction of the arrows 44 of FIG. 2;

FIGURE 5 is a cross sectional view corresponding to FIG. 4 illustrating a modification thereof;

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FIGURE 6 is a cross sectional view similar to FIG. 2 showing a further modification of the invention; and

FIGURE 7 is an enlarged cross sectional view of a portion of FIG. 6 taken on a plane indicated by and and viewed in the direction of the arrows 77 of FIG. 6.

In general, the invention relates to a convergent-divergent nozzle construction having a throat portion made up of a number of axially stacked thin cylindrical sections each containing'a solid coolant. In one embodiment, each section consists of a refractory metal washer to which are secured a plurality of refractory metal wires disposed flat against the washer in a spoke-like manner so as to be circumferentially spaced from each other.

The spaces between wires are filled with a solid coolant which is vaporized by the heat of operation of the nozzle. The heat of the exhaust gases is transferred through the refractory metal washers and wires to the coolant causing it to flow out onto the throat surface as a gas to cool it. In another embodiment, each section consists of an annular washer to which is secured a cylindrical porous refractory metal block, the pores of which are impregnated with a solid coolant adapted to flow out onto the nozzle throat surface as a gas to maintain it cooled. In both embodiments, the density of the coolant in each section can be varied to vary the pressure of expansion of the coolant to match the pressure of the exhaust gases at any particular point in the nozzle.

More specifically, FIG. 1 shows a fixed or nonorienting nozzle 10 of the convergent-divergent type. It has a diverging conical exhaust gas exit portion 12, an annular throat or venturi portion 14, and a converging conical inlet portion 16 connected to the aft end of an annular casing 18. Casing 18 may constitute a portion of a rocket combustion chamber or may be the aft end of any other suitable reaction motor duct. The throat and exit portions may be formed integral with the converging portion, or, as shown in the figure, may be secured thereto by any suitable means such as flanges 20 and bolts 22.

As seen partially in FIG. 2, the converging portion 16 of the nozzle is formed with the proper internal contour and consists of a hollow conical block of heat resistant insulating material 24. It is flanged at 26 and joined to the throat portion 14 by an annular flanged shroud .28 cemented or otherwise secured to a cylindrical metal casing portion 30. The downstream edge 32 of casing 30 is likewise cemented or otherwise secured to the inlet end 34 of the hollow conical nozzle exit portion casing $6. A number of axially stacked carbon rings 38 are secured within the casing to insulate it against the heat of the exhaust gases, the internal surface of each ring having a heat resistant liner 40.

The construction described provides an annular groove 42 in the throat section between the converging and diverging portions for insertion of a throat insert 44 therein of a construction constituting the subject of this invention. Further details of the reaction motor and nozzle construction other than those directed to the throat insert per se will not be given since they are known and are unnecessary for an understanding of the invention.

The insert 44 consists of a large number of thin cylindrical sections 46 of varying radial extent axially stacked against each other. Each of the sections consists of a flat refractory metal washer or apertured plate 48 to which are secured, as by brazing or the like, a large number of circumferentially separated refractory metal rods or wires 50. The wires in each section are of the same diameter and lie flat against the face of the washer. They are radially disposed in a spoke-like manner to provide a tapered space 52 between the wires, the spaces increasing progressively in width towards-the outer edge of the washer. The radially inner ends 54 of the wires have 3: only a minute clearance between them providing metered openings 56 (FIG. 3) to control the flow of coolant out onto the nozzle throat surface in a manner to be described.

Each of the sections is adapted to be axially stacked (FIGS. 2 and 4) against the adjacent section with diametrically opposite portions of the wires engaging adjacent washers. The axial spacing of the washers is therefore determined by the diameter of the wires in each section. The stacked sections are axially aligned with each other at their outer radial edges and secured within casing portion 30 by means not shown in a manner to seal the outer ends 58 of the tapered spaces 52. Each of the sections is of a different radial length so that together their radially inner ends form the desired convergent-divergent cross sectional shape of the throat 14.

The tapered spaces 52 between the wires and adjacent washers each contains a solid cooling medium 60, such as lithium or any well known synthetic polyamide resin, of which nylon is an example, which is released as a vapor in a manner to be described to flow out onto the throat wall of the nozzle to cool it. Nylon is an excellent coolant since it degrades to a low molecular wei ht gas at a temperature, 2000 F., for example, below that of the temperature at which an uncooled nozzle normally operates, which is approximately 6500 F.

In operation, the exhaust gases pass through the nozzle and are expanded out the exit portion 12. In doing so, their heat is initially transferred through the washers 48 and wires 50 to heat the coolant 60 in spaces 52. Subsequently, as the throat becomes hotter, and using nylon as an example, the nylon degrades into a gas. Since the spaces 52 are effectively closed by being sealed at one end and having metered openings at their other ends, the expanding gas causes an instantaneous pressure build-up to occur in the spaces 52. As a result, the coolant will boil out of the spaces 52 through the metered openings 44 onto the throat surface 62 (FIG. 3) to provide a thin layer of coolant between the exhaust gases and nozzle wall.

It will be clear of course that the axial thickness of each section, as determined by the wire size, will be so chosen that the volume of coolant initially provided will upon vaporization produce a pressure great enough to overcome the exhaust gas pressure at that point in the throat opposite the section. The pressure differential therefore permits the coolant to be boiled out onto the throat surface and be carried aft by the exhaust stream.

In the particular embodiment shown in FIGS. 1-4 where each section is of the same wire diameter, the minimum radial length and wire diameter of the sections effecting the desired coolant pressure would be predicated on the size of the first section 66 since the exhaust gas pressure is highest (500 p.s.i., for example) at this point in the nozzle and decreases progressively towards the throat. It is to be noted however, that, in the sections opposite the throat which contain more coolant by volume because of their added radial length, the circumferential spacing of the wires in each section and the size of the metered openings could be varied .so as to match the coolant pressure more closely to the exhaust gas pressure to assure a more uniform flow of coolant over the entire axial length of the throat liner.

From the foregoing, there-fore, it will be seen that the nozzle is maintained cooled at all times by the boiling out of the coolant onto the throat surface from each of the sections.

FIG. 5 shows a modification of the FIGS. 1 through 4 constructions illustrating a progressive variation of wire size and coolant volume in the different sections over the axial length of the throat insert to progressively vary the pressure of expansion of the coolant from one section to the other. In this manner, each section is fabricated with only that quantity of coolant necessary to provide an expansion pressure sufficient to overcome the particular nozzle operating pressure at that point in the nozzle. This results in thick sections at the inlet to the throat, progres- :sively thinner sections towards the throat proper and progressively thicker sections towards the outlet end of the nozzle. Since the other details and operation of this embodiment are similar to those of the FIGS. 1 through 4 construction, they will not be repeated.

The construction shown in FIG. 5 is not only easily manufactured, but also provides an infinite control of the volume of coolant in each section and therefore an infinite control of the pressure of expansion of the coolant. Therefore, each section is matched so as to provide a slight pressure differential between the coolant and the exhaust gases at that point in the nozzle. Only the minimum amount of coolant need be provided, therefore rendering the nozzle lighter.

It is to be noted that it is within the scope of the invention to change the radial length of each section rather than to change the axial thickness as described to match the coolant and nozzle gas operating pressures. This of course could be easily accomplished by contouring the inner wall of casing 30 to match the changed axial contour of the outer ends of the sections.

FIGS. 6 and 7 illustrate another embodiment of the invention which differs from the nozzle of FIGS. 1 through 5 only as to the details of construction of the throat insert 44-. In FIG. 6, the throat insert similarly consists of a number of axially stacked cylindrical sections 46 axially aligned at their radially outer peripheries, their inner radial ends being contoured to provide the desired cross sectional convergent-divergent shape of the throat passage.

Each of the sections consists of an annular refractory metal plate or washer 48' to which is bonded or otherwise secured a cylindrical block 68 of porous refractory metal material having its pores impregnated with a solid coolant. The porous block could be, for example, of tungsten or the like having forty percent voids filled with solid coolant, such as nylon or lithium. As in the FIG. 5 construction, the thickness of each section would vary to match the coolant expansion pressure to the particular nozzle operating pressure at that point in the nozzle. Additionally, the porosity of the tungsten blocks could be varied to also vary the coolant flow pressure.

Therefore, the initial sections 66' at the inlet to the throat would be thickest, the sections at the throat proper progressively thinner, and the sections at the nozzle outlet progressively thicker. Thus, the proper pressure differential will be provided between the coolant and the exhaust gases at each point in the nozzle to flow the coolant out onto the throat surface upon its vaporization by the heat of operation of the nozzle. In all other respects, the FIGS. 6 and 7 construction operates in a manner similar to that of the FIGS. 1 through 5 construction. The flow of exhaust gases through the nozzle initially transfers the heat of the gases through the refractory metal washers and the porous tungsten blocks to heat the nylon coolant and convert it int-o a gas. The coolant therefore expands and flows out of the sections onto the throat surface to provide a thin layer of coolant between the exhaust gases and the throat wall.

From the foregoing, therefore, it will be seen that this invention provides a nozzle construction containing a coolant in its solid state vaporized by the heat of operation of the nozzle to cool the nozzle. It will also be seen that the cooling system of this invention is highly reliable and eliminates the use of control systems, outside storage tanks, and other additional hardware common to liquid cooled nozzle constructions. It will also be seen that the nozzle construction of this invention utilizes readily available refractory material forrns, and affords an opportunity to vary coolant percentage loading to suit heat flux requirements by varying wire length and diameter or porosity. It will also be seen that the construction described permits dividing a nozzle into any required number of coolant pressure chambers to satisfy pressure distribution considerations, and that the thin sections will have good thermal shock resistance. Furthermore, in the construction described, it will be seen that the initial heat transfer to the coolant is high and slow-s as the coolant to wire or porous block volume increases permitting the use of less material since the inner nozzle wall temperature will increase slowly and can be allowed to approach a maximum at the end of the operation. And finally, it will be seen that this construction provides a lightweight design having an easily controlled porosity.

While the invention has been illustrated for use in connection with a rocket motor casing, it will be clear that it would have uses in many installations other than those illustrated, and that many modifications and changes may be made thereto without departing from the scope of the invention.

We claim:

1. A reaction motor cooled exhaust nozzle of the throated convergent-divergent type, the throat portion of said nozzle having a liner secured therein, said liner comprising a plurality of axially stacked radially disposed thin sections sealed at their radially outer peripheries, each of said sections comprising an annular flat refractory washer having a plurality of radially extending circumferentially spaced refractory wires secured along the face of said plate in a flat spoke-like manner, the spaces between the wires containing a solid coolant fusible at a temperature lower than that of the exhaust fluid passing through the nozzle, the securing of said sections in said throat sealing one end thereof, the heat of the exhaust fluid passing through the nozzle into contact with said sections melting and expanding the coolant therein, the pressure of expansion of said coolant in said spaces being greater than the pressure of the exhaust fluid passing through the nozzle to effect flow of the coolant onto the throat surface to cool it.

2. A nozzle as in claim 1, wherein the wires of different sections vary in diameter with respect to the Wires of the other sections to vary the axial thickness of each section and the volume of solid coolant contained between the Wires to thereby vary the expansion pressure of the coolant in each section.

3. A nozzle as claim 1, wherein the washers of adjacent sections are axially separated by the diameters of the wires therein, the wires of axially succeeding sections varying progressively in diameter with respect to the wires of the other sections to progressively vary the axial thickness of each axially succeeding section and the volume of solid coolant contained between the wires to thereby progressively vary the expansion pressure of the coolant in each section.

'4. A nozzle as in claim 1, wherein the radially inner ends of said wires of each section are spaced circumferentially from each other an amount providing metered openings between the wires for control of the coolant flow onto the nozzle inner surface.

S. A nozzle as in claim 1, wherein the radial inner extent of the washers and wires and coolant of each section varies with respect to adjacent sections to form the internal contour of said nozzle and vary the expansion pressure of the coolant in each section.

References Cited by the Examiner UNITED STATES PATENTS 2,926,490 3/1960 Eaton -3966 X 3,014,353 12/1961 Scully et al. 3,022,190 2/ 1962 Feldman. 3,073,111 1/1963 Hasbrouck 6035.6 3,089,318 5/1963 Hebeler 60-35.6 3,115,746 12/1963 Hsia 6035.6 3,137,995 6/1964 Othmer et al 6035.6 3,142,960 8/1964 Bluck 6035.6

FOREIGN PATENTS 578,007 6/ 1946 Great Britain. 871,346 6/ 1961 Great Britain.

CARLTON R. CROYLE, Primary Examiner.

SAMUEL FEINBERG, MARK NEWMAN, Examiners. 

1. A REACTION MOTOR COOLED EXHAUST NOZZLE OF THE THROATED CONVERGENT-DIVERGENT TYPE, THE THROAT PORTION OF SAID NOZZLE HAVING A LINEAR SECURED THEREIN, SAID LINER COMPRISING A PLURALITY OF AXIALLY STACKED RADIALLY DISPOSED THIN SECTIONS SEALED AT THEIR RADIALLY OUTER PERPHERIES, EACH OF SAID SECTIONS COMPRISING AN ANNULAR FLAT REFRACTORY WASHER HAVING A PLURALITY OF RADIALLY EXTENDING CIRCUMFERENTIALLY SPACED REFRACTORY WIRES SECURED ALONG THE FACE OF SAID PLATE IN FLAT SPOKE-LIKE MANNER, THE SPACES BETWEEN THE WIRES CONTAINING A SOLID COOLANT FUSIBLE AT A TEMPERATURE LOWER THAN THAT OF THE EXHAUST FLUID PASSING THROUGH THE NOZZLE, THE SECURING OF SAID SECTIONS IN SAID THROAT SEALING ONE END THEREOF, THE HEAT OF THE EXHAUST FLUID PASSING THROUGH THE NOZZLE INTO CONTACT WITH SAID SECTIONS MELTING AND EXPANDING THE COOLANT THEREIN, THE PRESSURE OF EXPANSION OF SAID COOLANT IN SAID SPACES BEING GREATER THAN THE PRESSURE OF THE EXHAUST FLUID PASSING THROUGH THE NOZZLE TO EFFECT FLOW OF THE COOLANT ONTO THE THROAT SURFACE TO COOL IT. 